Composite compositions

ABSTRACT

Ferrophosphorus containing at least 1 percent silicon by weight is admixed with calcium carbonate and formed into an integral composite, the silicon content of which is converted to silica upon addition of the composite to molten iron, steel, or alloys thereof. The composite provides, for example, a useful effective low silicon source of phosphorus and alloying constituents for iron, steel and their alloys.

United States Patent 1191 Stenzel 1 51 Feb.27,1973

[ COMPOSITE COMPOSITIONS [75] Inventor:

Assignee:

Filed:

Hans-Jurgen A. Stenzel, Brentwood,

Monsanto Company, St. Louis, Mo.

June 29, 1970 US. Cl, ..75/132, 75/56, 23/106 Int. Cl ..C2lc 7/02, C221) 5/00 Field of Search ..23/37, 52, 110; 75/53, 57,

References Cited UNITED STATES PATENTS Miller ..75/132 Barr ..23/223 X White ..75/132 X Brenek ..23/110 R X I Neumark ..75/132 2,476 ,418 7/1949 Klugh ..75/132 977,819 12/1910 Mehner ....75/28 X 987,554 3/1911 Coggeshall ..75/3

2,320,342 6/1943 Bridger ..75/28 X 3,125,438 3/1964 Franklin et a1, ..75/3

Primary Examiner-Dewayne Rutledge Assistant Examiner- 1. E. Legru Attorney-Herbert B. Roberts, Thomas N. Wallin and Neal E. Willis [5 7 ABSTRACT composite provides, for example, a useful effective low silicon source of phosphorus and alloying -constituents for iron, steel and their alloys.

6 Claims, No Drawings COMPOSITE COMPOSITIONS BACKGROUND OF THE INVENTION This invention relates to composite compositions of ferro and non-ferro alloys useful in the metalurgical industries. A particularly preferred embodiment of this invention relates to composite compositions of ferrophosphorus suitable for use in the steel industry in the formation of phosphorus containing steels.

Ferrophosphorus is a by-product of the well-known electric furnace processes for production of elemental phosphorus. Depending upon the compositions of ore fed to the furnace, the ferrophosphorus generally consists of to 30 percent phosphorus, from 55 to 80 percent iron and, in some instances, minor amounts of chromium, vanadium, titanium, manganese and nickel, etc. In addition, ferrophosphorus, particularly that derived as a by-product of the processing of phosphorus ores from the south-eastem part of the United States, often contains silicon in amounts up to 8.0 percent.

The addition of ferrophosphorus to molten iron, steel, and alloys thereof is a convenient means of incorporating desired phosphorus contents into steel alloys. However, since silicon (or ferro-silicon) is soluble in molten metals and affects their properties, it is often desired that the ferrophosphorus used for such purpose has a silicon content less than 1 percent by weight, preferably less than 0.5 percent by weight or less. Accordingly, for such use, it has hitherto been necessary to select ferrophosphorus characterized by low silicon content as a result of the assay of the raw materials fed to the phosphorus furnace. Alternatively, ferrophosphorus having high silicon content can be processed to remove the silicon or convert the silicon to innocuous silica (which is insoluble in the molten metal). Unfortunately, such disiliconization treatments have hitherto proven undesirably expensive.

The presence of silicon in ferrochromium, ferronickel, ferromanganese, copper-nickel alloys and other ferro and non-ferro alloy materials presents similar problems.

SUMMARY OF THE INVENTION It is the object of this invention to provide a composite composition containing high silicon content metallic alloys, such as ferrophosphorus, which can be added to steel formulations without unduly increasing the silicon content thereof.

Basically, the compositions of this invention comprise particulate metallic alloy materials less than 4 mesh 'U. S. standard sieve size having an elemental silicon (the term "elemental silicon" is used herein to exclude oxidized silicon--i.e., silica,but to include silicon alloyed or chemically associated with metallic components e.g., ferro-silicon) content of at least 1.0 percent by weight, admixed and in adherent contact with a quantity of calcium carbonate (which functions as an oxidizing agent) sufficient to convert a major proportion of the silicon to silica. In one embodiment of the invention, such composition is provided as a shaped, integral form particularly convenient for use in metallurgical industries.

The invention will be better understood from the following description of the preferred embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The compositions of this invention provide alloying ingredients of "effective low silicon content (even though actual" silicon content is high, addition of the compositions to molten metal baths does not result in an equivalent increase in silicon content since a major proportion of the silicon is converted to silica).

The term alloying ingredient is used to include ferroalloys such as ferrophosphorus, ferro-nickel, ferrochromium, ferro-vanadium, ferro-manganese, etc., and non-ferroalloys such as copper-nickel alloys which in the metallurgical industries are added to, for example, molten iron or steel to provide a desired phosphorus, nickel chromium, etc., content or used as raw materials for non-ferroalloys. The alloying ingredient must, of

course, consist of a component or components less readily oxidizable than silicon.

For the sake of conciseness, the compositions of this invention are described herein with reference to ferrophosphorus as the alloying ingredient but it is to be understood that the teachings are, likewise, applicable when other alloying ingredients or mixtures thereof are utilized.

A representative composition of this invention comprises ferrophosphorous containing silicon (probably present as ferro-silicon) and calcium carbonate.

United States Pat. application Ser. No. 18,317 filed Mar. 10, 1970 and a continuation-in-part thereof Ser. No. 43,965, filed June 5, 1970 and now abandoned disclose the utility of composite compositions of ferrophosphorous and solid oxidizingagents as additives to molten metals. Prior to the invention described in these applications it would have been expected that upon addition of such compositions to molten metals, the silicon, iron, and phosphorous contained in the composition would be immediately separated from the oxidizing agent before any substantial conversion of silicon to silica would take place. Further, from the referenced disclosures, one would expect that calcium carbonate in view of relatively low thermal stability would not be a satisfactory oxidizing agent.

' However, when the compositions of this invention are added to molten steel or steel alloy, it is unexpectedly found that the silicon content of the composition is substantially completely oxidized to silica. In order to obtain this surprising and advantageous result, it is essential that the composition possess certain critical characteristics as hereinafter discussed.

The ferrophosphorus contained in the composition must be less than 4 mesh U. S. standard sieve size, preferably less than 30 mesh or even smaller. If larger particles of ferrophosphorus are utilized, the conversion of the silicon content of the ferrophosphorus to silica upon addition of the composition to molten steel or steel alloy is low even when excess oxidizer is employed. The ferrophosphorus utilized in the invention will contain at least 1 percent by weight silicon and generally substantially larger amounts, up to 8 percent, it being emphasized, however, that there is no theoretical upper limit on the silicon content.

The oxidizing agent used in the compositions of this invention is calcium carbonate. This material in addition to functioning as an effective oxident, is highly desirable from the standpoint of availability and cost.

In view of the high melting point of the silica calcium oxide slag formed in the reaction. 2 CaCO +Si SiO,+2baCaO+2CO, it is generally desirable incorporate a sufficient amount of flux, e.g. CaF,, SiO,, Al,O or iron oxide, in the composition to lower the slag melting point. For example the composition may advantageously contain Cal equivalent to 30 percent, SiO, equivalent to 25 percent or FeO equivalent to 60 percent of the weight of CaCO Higher iron oxides Pep, or Fe O can advantageously serve as a source of flux and as a supplementary oxidizing agent. A particularly preferred combination for admixture with the ferrophosphorus consists of from 80 to 20 percent CaCO and 20- 80 percent iron oxides.

The amount of calcium carbonate which must be composited with the ferrophosphorus to convert the desired amount of silicon to silica is readily determined by routine testing. When the ferrophosphorus is finely divided, the actual oxidizer requirements approximate stoichiometric requirements. When the ferrophosphorus is coarser, excess oxider is required. The use of finely divided (less than 30 mesh, preferably less than 100 mesh U. S. standard sieve size) ferrophosphorus to avoid necessity of wasteful oxidizer excesses is preferred.

It is essential that the ferrophosphorus, calcium carbonate and flux be thoroughly admixed and composited so that upon addition to a molten metal bath, the calcium carbonate will remain in integral contact with the ferrophosphorus for a length of time sufficient to effect oxidization of the silicon contained therein.

Integral compositing can be conveniently obtained by admixing the particulate ferrophosphorus with calcium carbonate and flux and dampening the mixture so that the oxidizing agent adheres to the ferrophosphorus particles. The composite is then dried, leaving the oxidizing agent in adherent contact with the ferrophosphorus particles. In drying, it is desirable to use conditions adequate to completely remove water in order that undue rapid disintegration of the composite does not take place upon its addition to molten metal.

Alternatively, integral compositing can be effected by pelletizing or briqueting mixtures of ferrophosphorus, flux, and oxidizing agent in accordance with conventional procedures. If desired, a binder can be incorporated in the mixture to improve pellet or briquette strength. Conversion of the composition of this invention into pellets, briquets, or other shaped forms is particularly desirable for convenience in handling.

The composition of this invention and their use are further illustrated by the following examples wherein all parts and percentages are by weight.

EXAMPLE I A shaped composite composition is prepared as follows:

About 275 parts calcium carbonate (less than 20 mesh U. S. standard sieve size) is admixed with about 1000 parts ferrophosphorus (assaying about 22.5 percent P; about 3.4 percent Si and being less than 100 mesh U. S. standard sieve size). These proportions correspond to percent excess of the theoretical requirements for conversion of the Si to SiO The mixture is compressed at about 5000 psig into cylindrical pellets about 1 inch in diameter and about 1 inch long.

The pellets are added to molten steel which 15 then EXAMPLE I] A shaped composite composition is prepared as follows:

About 76 parts Pe o. and 132 parts CaCO (less than mesh U. S. standard sieve size) are admixed with 1000 parts ferrophosphorus identical to that utilized in Example I. The mixture is pelletized as in Example 1. Addition of the pellets to molten steel results in a ratio of (increase in phosphorus content)/increase in silicon content) of about 42.

The slag formed was observed to be much less viscous than in Example I demonstrating the desirability of using a fluxing agent.

Results similar to those discussed above are obtained when other alloying ingredients are substituted for ferrophosphorus.

What is claimed is:

l. A composite composition comprising particulate ferrophosphorus less than 4 mesh U.S. standard sieve size having an elemental silicon content of at least 1.0 percent by weight, said ferrophosphorus being admixed and in adherent contact with sufficient calcium carbonate to convert at least a major proportion of the said silicon to silica.

2. The composition of claim 1 wherein said ferrophosphorus is less than 30 mesh U. S. standard sieve size and said composition contains an amount of said calcium carbonate sufficient to convert substantially all of said silicon to silica.

3. A composite composition having a shaped, integral form and comprising particulate ferrophosphorus less than 4 mesh U.S. standard sieve size having an elemental silicon content of at least 1.0 percent by weight substantially uniformly admixed with sufficient calcium carbonate to convert at least a major proportion of said silicon to silica.

4. The composition of claim 3 wherein said ferrophosphorus is less than 30 mesh U. S. standard sieve size and said composition contains an amount of said calcium carbonate sufficient to convert substantially all of said silicon to silica.

5. The composition of claim 3 additionally containing a fluxing agent.

6. The composition of claim 5 wherein said fluxing agent is an iron oxide selected from the group consisting of Fe,O Fe O and mixtures thereof, said fluxing agent being present in an amount equal to from 20-80 percent of the weight of said calcium carbonate. 

2. The composition of claim 1 wherein said ferrophosphorus is less than 30 mesh U. S. standard sieve size and said composition contains an amount of said calcium carbonate sufficient to convert substantially all of said silicon to silica.
 3. A composite composition having a shaped, integral form and comprising particulate ferrophosphorus less than 4 mesh U.S. standard sieve size having an elemental silicon content of at least 1.0 percent by weight substantially uniformly admixed with sufficient calcium carbonate to convert at least a major proportion of said silicon to silica.
 4. The composition of claim 3 wherein said ferrophosphorus is less than 30 mesh U. S. standard sieve size and said composition contains an amount of said calcium carbonate sufficient to convert substantially all of said silicon to silica.
 5. The composition of claim 3 additionally containing a fluxing agent.
 6. The composition of claim 5 wherein said fluxing agent is an iron oxide selected from the group consisting of Fe2O3, Fe3O4 and mixtures thereof, said fluxing agent being present in an amount equal to from 20-80 percent of the weight of said calcium carbonate. 